Test fired my 8" 9mm with suppressor (Omega 9K) a few days ago using the stock carrier configuration (no weight).  Bryan at CMMG had advised that I might need to add some weight and he was correct.  Using 147gr Lawman and 147gr Federal HST I had a few FTE.  This rifle works 100% without the can.  I had some not-quite-factory 125gr reloads on hand and had no functional issues with this ammo and the can.  Weight kit is on the way.  You would think during the 8 month wait I would have been smart enough to get the weights in hand.

No way I intend to run this without muffs, but the can looks "cool" and I'm excusing the extravagance based on avoiding additional hearing damage in the event of a home break-in.  Sucks as an excuse, but you've got to some up with something.

What buffer and spring combo are you using?

As mentioned on my site: http://www.c3junkie.com/?page_id=280
If I use a their stock 9mm bolt and my preferred, tube/spring/buffer config, I'm not having any issues running with no weight in the carrier.

I also went to a SMG match this past weekend and let another shooter that normally runs semi (as he doesn't have a full auto lower) run the entire match with his personal CMMG 9mm upper on my lower.  He doesn't have the weight in the carrier and he ran all 4 stages with zero malfunctions....oh and he was using an Omega 9K as well.

I had my A5 tube on the lower, RB5007 and Tubb 556 flat spring in the lower.

I will say that I do see a noticeable increase in cyclic rate when running a suppressor on the 9mm and .40SW CMMG RDB's....like around 60 RPM increase.  While there is virtually no increase with the .45ACP CMMG RDB.

That is one reason I started messing with modifying 5.45 bolts with my own angles to slow down the cyclic rate and increase the delay.  
Currently I'm using a factory CMMG .40 SW RDB bolt in 9mm instead of throwing mass at the issue.

Amphibian, thanks.  Unsuppressed I'm running carbine buffer/spring and stock upper without issue in both of my 8" rifles.  I know I could tweak the buffer without having to add weight, but I'd have to make my two lowers identical since my HD rifle is a backup for what I use in competition.  I'll consider the buffer setup though.  BTW, was that other fellow running subsonic ammo as well?  My setup seemed to cycle fine with supersonic, but for HD I'm going with subsonic.

He was using super sonic but I have tried factory and reloaded subsonic and I still don't need any weights with this buffer/spring setup.

I should never has posted this question.  I'm such a geek in real life that I don't think I'm going to be able to resist a new buffer setup (x2).  Thanks, Amphibian

I use it for sbout 90% of my configurations

Please let me know what weight you use.
I have the Banshee on order as well to use with my Omega 9K.  I ordered the action tune kit with my lower.

I ended up ordering the upper and lower separate.  The lower will sit at my FFL while I eform 1 it and I can play with the upper using some Endomags.

I'm going to be running 147gr FMJ subsonics and some 158/165gr FMJs as well.

My plan is to put Amphibians configuration into one of my lowers and try in various configurations: supersonic and subsonic each with and without can.  If those configurations work I'll duplicate the hydraulic buffer configuration in the other lower and call it good.  Bryan at CMMG did say that with the can I might need a weight; I'm sure he was thinking of the smallest 2 oz. weight.  Should have what I need in a few days so I'll be able to test out no later than next week.

Im running a banshee 9mm with a rugged obsidian and have had zero issues. I use the tuning kit with the middle sized weight. Works like a charm.

I have no doubt the added weight works, but I want to keep both my lowers in the same configuration and I don't need the weight for my competition load sans suppressor.

why not? is it loud? curious because i was under the impression that the radial delayed blowback should suppress very well..

Mine suppresses very well....on par with my MP5.
The guy that was using my lower with his 5" CMMG RDB + Omega9K was running supersonics and so it was loud.  I also heard an Omega 9K on one of my 8" uppers using subsonics and it definitely wasn't as quiet as one of my can's pictured above but not too bad.

I don't own an Omega 9K so can't comment too much on what I've already posted....I just know I don't use hearing pro w/ my cans w/ my CMMG RDB setups.  9mm / .40SW and .45.  They are all pretty quiet to me.

Worked as Advertised:
Shot a bunch of different loads suppressed and un-suppressed using a BCM A5 buffer tube, Tubbs 5.56 flat wire spring and the RB5007.  Everything worked including  147gr Lawman, softer 145gr coated loads and both 115gr and 124gr supersonic loads.  I'll modify my second lower and I'll be good to go.  Thanks Amphibian.

Great to hear!  Not only does it 'work'...I'd hope you also noticed a considerable reduction in the recoil impulse.  You should also notice it smooth out your 556 configuration as well.

Absolutely softer shooting:).  Thanks again.

So as not to start a new thread I'll tack on one additional note:

I check with Bryan at CMMG and he said that +P and +P+ were GTG.  I've sourced some 124gr Federal HST +P and I'll verify function.  Might be what I use as in an alternate mag for longer range.  I'll update this post with results when I have the ammo in hand.

I ran a mix of various HP's including Federal in full auto and Endomags with no issues.

I have a case of Winchester Ranger 127gr +P+ in my locker at work. I'll test those when my Banshee gets built.

Got my Banshee upper today. Didn’t make it 60 rounds.

Extractor broke. Spring lost.

Where did it break?  Did the claw that grabs the rim of the case snap off?  Which spring got lost?  Extractor?

I have only had the extractor crack near the pin on me as well as other issues which I believe were caused by excessive headspacing on the barrel.  I have it documented in this video.  I also demonstrate how you can determine (IMHO) if your barrel has excessive headspacing.  CMMG swapped my barrel for me.

@Chowser, did this failure occur with +P+.  If not, which ammo.  Bryan at CMMG did suggest that for hotter loads I should have a set of carrier weights on hand.  I have tried +P without this, this with @amphibians buffer setup.  Even if +P+ I don't know that the increased pressure and bolt speed would have put more stress on the extractor.

@Chowser, did this failure occur with +P+.  If not, which ammo.  Bryan at CMMG did suggest that for hotter loads I should have a set of carrier weights on hand.  I have tried +P without this, this with @amphibians buffer setup.  Even if +P+ I don't know that the increased pressure and bolt speed would have put more stress on the extractor.  My main interest is subsonic, but I was exploring +P as a more effective round for longer distance SD.  Turns out that at 100 yards the info out there doesn't demonstrate a great deal of difference between subsonic and supersonic.

I never got to the hotter ammo. I was using winchester winclean 147gr fmj and an Omega 9k suppressor.

I haven’t gotten around to taking it apart. Here’s a pic. Spring is lost to the wind.
I have the action tuning kit ordered but I ordered it with my lower which hasn’t hit production yet.



I emailed CMMG a pic and they are sending me replacement parts.


But I did order the bolt maintenance kit and two mk10 springs with the upper so those should be in the box.

Hopefully I will get this back up and running before I get back to work on Saturday.
Before it broke, it did run beautifully.

When I experienced some FTE issues out of the box CMMG was very good about getting me replacement parts.  I don't know to what extent they depend on suppliers versus in house, but I suspect their seeing some component "escapes" in their supply chain.  I had one firing pin mushroom: easily replaced either from CMMG or standard AR part.  I think the initial ejector springs in my two bolts were not the Mk10, but that's was easily remedied.

I'm also using an Omega 9K.  Bryan had mentioned that I might need a bit of carrier weight running suppressed, but I never test the rifle with the carbine setup, instead opting to go with @Amphibians A5 buffer tube with a Kynshot RB5007 hydraulic buffer.  This setup does work suppressed and non-suppressed with every ammo I've tried.

I'm using WSF powder behind 147gr coated bullets in my competition rifle, probably a bit under factory loads.  I've gotten religious about cleaning since in my case the WSF is a bit dirty.  Once you get things running smoothly don't hesitate to take the bolt apart if things look dirty on the outside; easy enough to do and you might find a lot of build-up in the ejector channel, also under the extractor claw.